The ultrastructural changes of the tissues of musculo-aponeurotic layer of anterior abdominal wall after implantation of the “lightweight” and “heavyweight” polypropylene meshes into the retrometallic space were studied in the experiment. Significant differences of the tissue reactions at different periods of the experiment on the implanted material were evidenced. The presence of a moderately pronounced inflammatory tissue reaction was noticed on the 14th day of the study in the area of the implantation of the “lightweight” polypropylene mesh compared to the “heavyweight” one: the inflammatory response included acute manifestations of aseptic inflammation with a significant tissue response. On the 28th day of the experiment, in cases of implantation of the “lightweight” mesh, the stabilization of tissue reaction to the implant with reduction of inflammatory changes was observed, as evidenced by a significantly smaller number of leukocyte infiltration sites, a significant improvement in vascularization and development of collagen fibres around the mesh material with fibroblasts, which was not observed in the area of implantation of the “heavyweight” polypropylene mesh. The conducted morphological and ultrastructural studies have prioritized the use of “lightweight” meshes when choosing material to perform allohernioplasty.